1. Field of the Invention
The present invention relates to a system and method for controlling a display of graphics data having a pixel aspect ratio on a video monitor having a different display aspect ratio than the pixel aspect ratio. In particular, the present invention relates to a system and method for controlling a display of mixed images of the graphics data and motion picture data on a television monitor with a canceling of the difference between the aspect ratios.
In addition, the present invention relates to a system and method for controlling a display of images of non-interlaced graphics data on an interlaced video monitor by canceling a difference between respective aspect ratios.
Furthermore, the present invention relates to a system and method for controlling a display of graphics data having a particular pixel aspect ratio on a video monitor having a different display aspect ratio without any distortion of the graphics data pixels.
2. Discussion of the Background
In recent years, in accordance with development of computer technologies, a variety of digital devices, such as digital video players or set-top-boxes, have been developed for use with an in-home television (TV) receiver used as a monitor for displaying computer graphics data, video etc. These type of digital devices control reproduction and display of mixed data including computer graphics data and motion picture data stored on a media. The mixed data is typically stored on the media as compressed data using digital compression coding. An optical disk, such as a compact disk (CD) or a digital versatile disk (DVD), are typically used as the data storing media.
The DVD utilizes a new standard for coding of a video information, such as a movie, in order to store a large amount of data on a small disk space. For example, a DVD coded full-length movie could be stored on a DVD the size of a standard CD (typically 640 MB) with a high quality. The new coding standard for the coding of DVD video information is referred to as motion picture experts group 2 (MPEG2) coding. For storing large amounts of high quality image data on the DVD disk, the MPEG2 coding for the DVD basically utilizes a variable rate coding technique for recording and reproducing the video data.
The amount of image data that can be stored on a DVD using the variable rate coding is dependent upon characteristics of the image data. Image data that is made up of scenes having a lot of motion require a greater amount of storage than scenes with lesser motion. The stored motion picture data in the DVD are basically reproduced using image signals of a particular television standard, such as National Television System Committee (NTSC) standard, Phase Alternation by Line (PAL), standard, etc. Consequently, the video data reproduced from a MPEG2 decoder are provided as non-interlaced picture signals to a video monitor.
In addition, recent developments in computer technology have made it possible to increase operational speeds of central processing units (CPUs) and graphics controllers. Accordingly, a higher grade of graphics data, such as three dimensional graphics, can be displayed on a television monitor by using a digital video player or a set-top box. That is, the users of the set-top box can interactively change the displayed images on the video monitor by varying the graphics data in various forms. In this way, a display of mixed high grade images comprising graphics data and motion picture data is now possible.
However, it is typically not possible to reproduce mixed images of graphics data and video data on a television monitor with improved graphics data quality. Displaying non-interlaced computer graphics data on an interlaced television monitor, results in the following problems:
(1) Differences between graphics data pixel aspect ratio and video monitor display aspect ratio:
Computer graphics data usually have a pixel aspect ratio of 1 to 1 (1:1). In contrast, a video or television monitor has a different display aspect ratio than that of the graphics data pixel. The television monitor usually has a display ratio that is wider in a horizontal direction than in a vertical direction (e.g., 16:9 or 4:3). As result of this, when the graphics data are displayed on the television monitor, without modification, the reproduced graphics data are displayed in a distorted form rather than in the original form. For example, if a circle comprises the graphics data having a given pixel aspect ratio for display on a non-interlaced computer monitor, when the circle is reproduced on an interlaced video or television monitor having a horizontally wider aspect ratio, the circle is displayed as a vertically elongated ellipse on the television monitor.
(2) Differences of signal bandwidths of interlaced and non-interlaced monitors:
A television monitor utilizes an interlaced scanning display or monitor. On the contrary, a computer uses a non-interlaced scanning display. The graphics data displayed on the non-interlaced scanning monitor have wider bandwidths for brightness and color signals than the bandwidths for brightness and color signals for a motion picture (video) data. These bandwidth difference of brightness and color signals between the graphics data and the motion picture data, result in flickering of the reproduced computer graphics data on the television monitor.